[RTTY] PSK31 is faster (Was FD RTTY Question)

[Joe Subich, W4TV]

Again, why couple a better code to higher speed with poorer S/N
and wider bandwidth?  Why not stick with 45.45 baud and compatibility
with all the MMTTY/Windows installations linked to EXTFSK with its
fixed 45.45 baud rate (as well as compatibility with the 45.45 baud
specific RTTY filters in several transceivers)?

73,

    ... Joe, W4TV



On 6/27/2012 8:33 PM, Robert Chudek - K0RC wrote:
> The *BARTG High Speed Sprint* might be an existing (recently introduced)
> contest to make the transition?
>
> 73 de Bob - KØRC in MN
>
> ------------------------------------------------------------------------
> On 6/27/2012 3:43 PM, Paul Stoetzer wrote:
>> Somebody should set up an ASCII contest. That would be interesting.
>>
>> Paul, N8HM
>>
>> On Wed, Jun 27, 2012 at 4:36 PM, Kok Chen <chen at mac.com> wrote:
>>> On Jun 27, 2012, at 12:47 PM, Alex Malyava wrote:
>>>
>>>> Why don't we just invent/introduce some new RTTY standard -
>>>> the one with 6 bits instead of 5 - covering whole alphabet and digits
>>>> without any FIGS/LTRS and speed it up a little bit to compensate an extra
>>>> bit?
>>> There is no need to introduce another "mode du jour" even.
>>>
>>> 7-bit ASCII (CCITT ITA-5) RTTY has been FCC approved (see part 97.309(c)) for a long time now.  fldigi supports it, so does MultiPSK and cocoaModem, among others.
>>>
>>> In a discussion (a year or even longer ago) on this reflector, I had shown that for most RTTY contest exchanges, ASCII RTTY beats out Baudot RTTY in speed, even when both are running 45.45 baud.
>>>
>>> You get rid of the FIGS/LTRS confusion (thus problem with USOS incompatibility either; USOS is a Baudot problem), allows lower case, and it still beats out Baudot in contesting speed.  It is when sending paragraphs of upper case text that Baudot wins over ASCII.
>>>
>>> Because of the Teletype Models 33/35, the popular speeds for running ASCII RTTY was 110 baud.  At that speed, it will wipe the floor with Baudot RTTY.
>>>
>>>> Or drop one stop bit to save the length? Or use 3 frequency FSK -
>>>> shift left is "0", shift right is "1" and middle is sync/start/stop ?
>>> 3FSK may not be a good idea.  The reason is that the equalizer to compensate for selective fading will be at best very complex to build.
>>>
>>> 2FSK has the very unique ability to fight selective fading with a very simple thresholding scheme.  Once you add more tones, you can no longer build simple ATC circuits.
>>>
>>> For that reason, you will find that there is nothing in MFSK16 (16 tones), DominoEX (18 tones) or Olivia that explicitly fixes the selective fade problem -- they all use long interleaved codes to fight QSB in general -- and you may not want to use long interleavers with short contest exchanges; the latency will need to be over 1 second to be effective.  You will need to add latency to the exchange time.  Selective fading happens quite often.  You can almost not avoid it with a Rayleigh path.
>>>
>>> Anyhow, the solution is already at your fingertips, and the FCC has blessed it for years now.  It is called ASCII.  And 110 baud with 170 Hz shift is a breeze.
>>>
>>> 73
>>> Chen, W7AY
>>>
>>>
>>>
>>>
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